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  #1  
Old 06-03-07, 10:36 PM
David McKay David McKay is offline
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Default cadmium red pigment

Hi Friends:

I have a question for the pigment experts in our group. A friend of mine (who tried egg tempera then gave it up) gave me some of his left over pigments. Among them was a cadmium red deep. Since I had some of this pigment I never got around to using his for some time. Recently however, I took a closer look and realized that his cad. red deep was quite a bit darker than the one that I had been using for years. Also when I mixed it, it took more work and time to get it to settle into a "paint". I do not premix my pigments with water.

The two cad. red samples are from different manufacturers. I assumed however, that it was pretty much the same material, and therefore should react in the same way. Any ideas?? Maybe one of the pigment samples is mislabled??

David
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Old 07-03-07, 04:22 AM
JanMoore JanMoore is offline
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I have encountered this with different pigments. There doesn't seem to be a strict standard for pigment colors. This seems especially true with raw sienna. I don't think it's the material that is the problem with mixing, but the size of the particles. Larger particles have more surface tension so the particles won't dissipate. Try adding a drop of isopropyl alcohol to break that surface tension. (It will evaporate out and not change your paint at all. If your paint feels grainy after this, then you need to grind the pigment into smaller particles. (See my old post about Alizarin Crimson and grinding the pigment.)
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Old 07-03-07, 05:52 PM
Alessandra Kelley Alessandra Kelley is offline
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I don't work with Cadmiums (they're VERY toxic), but I hear that they can be stubborn to mix.

It is true that different batches of the same pigment can act very differently. This is true even for chemically-produced ones that you would think would be identical. I have had some amazing variations in Ultramarine Blue over the years.

Probably it's just one of those things.
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Old 07-03-07, 07:39 PM
lindapaul lindapaul is offline
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Default cad reds

To make cad reds behave, I add several drops of Clinique #2 skin toner and the pigment immediatley dissapates, then you can add a bit of water , then your egg yolk. This actually works better than alcohol which evaporates too quickly I find.
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Old 09-03-07, 04:41 PM
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Bert Congdon Bert Congdon is offline
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Default Cad Red

I had the same problem with viridian, but I grind them ahead with water and work from the paste. I "fix up" my water with oxgall (wetting agent) and Preventol from Kremer. No problem!
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Old 09-03-07, 07:39 PM
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PhilS PhilS is offline
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David,
Cadmium red is a beautiful color, but it absolutely refuses to mix with water. And, as Alessandra says, it's pretty toxic. As a result, I just don't use it. There was a discussion about cadmium red a while back. I recall someone saying that alcohol helps dissolve the pigment in water. Don't remember which kind of alcohol, though.
I basically use Venetian red, now. If I want it to have more zing, I add a little quinacridone red to it.
Phil
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Old 12-03-07, 01:06 AM
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jeff jeff is offline
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I use cadmium red at least sometimes and keep it wet in its container. Although it is slow to wet, it does eventually and just pouring in some distiled water in a well ventilated place outside and letting it sit for an hour or so soon wets it all. After that it is completely fine to use and treatments like alcohol are unnecessary. I have used small amounts of methylated spirits occassionally to wet a dry pigment. It mixes in water well so only a drop or two are needed when it is used. It just decreases the surface tension of the water. The problem with wet pigment is keeping it from drying out. Some pigments will turn into hard cakes if they are dried out and don't rewet well. Most are OK though. The best thing to do (speaking from my mistake here) is to not wet all your supply but take a smaller amount in a very well sealed container (like a plastic 35mm film container) and keep that wet as your working pigment. If your like me that would be a years supply probably.

jeff b
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Old 12-03-07, 03:16 AM
David McKay David McKay is offline
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Hi, Thanks for all of your replys. Actually, I was wondering why the difference between the cad. red deep and the other lighter cad. sample that I had used previously. Only the darkest one (which was from a different manufacturer, Grumbacher) gave me a problem when I mixed it with water. Not that it was impossible to mix, it just took longer and more mixing. The lighter cad. red (from D. L. Stevensons) mixed quite nicely.

Phil, I have never used Venetian red, but have always thought of trying it. I too use quinacridon red sometimes which is a wonderfully strong, clean colour. Another red that I have not tried is red ochre. Anyone have any thoughts on that pigment?? David
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Old 12-03-07, 01:28 PM
Alessandra Kelley Alessandra Kelley is offline
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I use Red Ochre. It has nicer handling properties than pure Iron Oxide Reds (which can solidify into cakes even when wet -- I keep my wet pigments under an extra layer of water to avoid the drying-out problem Jeff mentioned). It's a natural pigment, so different batches can vary a lot. I have one batch that is a little gritty, like Burnt Sienna, and another that is soft and almost slimy.

The color of Red Ochre is gentler than other related reds, and it's a little more transparent, good for flesh tones without garishness. I like Venetian Red too -- it is the natural Iron Oxide red closest to the artificial ones in strength.

I use pure Iron Oxides rather than any Cadmiums. If I want a brighter color, I'll glaze a red with Quinacridone Violet; for a bright yellow, I paint in a pale mixture of Yellow Ochre or Mars Yellow and white, then glaze it with Yellow Ochre. The effect is really quite good.
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  #10  
Old 17-03-07, 04:30 AM
JanMoore JanMoore is offline
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David -- I think the problem you had between these two Cads was the manufacturers. I've had some Grumbacher pigments that didn't mix as well as others. This relates to the size of the particles. You can try different brands or get recommendations from everyone in the forum. You'll find many people swear by Kremer (which I also like) but there, too, you'll encounter certain pigments that aren't ground finely enough. For my basic palatte, I like Gamblin.
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